Testing Production Sensitivity in a Constrained 3-D Fluvial-Estuarine Channel Complex, Trinidad

Grant D. Wach, Hasley L.G. Vincent, and Farrukh Akram
Dalhousie University, Halifax, NS

The Pliocene sediments of Trinidad have served as an important hydrocarbon reservoir target since the early 20th century, onshore Trinidad and over the past 30 years in the offshore Columbus Basin. Recent offshore discoveries have benefited from the application of 3D seismic, sequence stratigraphy and reservoir modelling techniques not applied to older producing onshore fields. These fields have been producing without 3-D seismic data and rely on techniques using outcrop and well log correlation for efficient reservoir production.

Outcrops within the Pliocene Springvale and Morne L'Enfer formations show a transition from tide dominated to fluvial environments within an overall deltaic setting and this linkage is apparent in the Stollmeyer oil sand quarry. Exposures within the quarry, essentially an exhumed oil field, provide an unparalleled opportunity to directly examine the 3-D architecture of a fluvial-estuarine channel complex and oil-water fault compartmentalization. Channel dimensions, lithofacies, net to gross, and reservoir heterogeneity data were input into the geological reservoir model.

Reservoir simulation studies were carried out to analyze the sensitivity of primary recovery to changes in reservoir architecture and engineering parameters. Variables included changes in channel morphology, permeability baffles and barriers, fault placement and sealing capacity in addition to well placement and completion methods.

The results of the study are directly applicable to subsurface production from producing fields within onshore and offshore Trinidad, as well as an analogue for similar geological environments elsewhere.